Charles e



(No Model.)

O. E. SCRIBNER. TELEPHONE LINE CIRCUIT.

No. 584,415. Patented June 15, 1897..

lJNiTnn STATES PATENT Curios.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE YVESTERNELECTRIC COMPANY, OF SAME PLACE.

TELEPHONE-LINE CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 584,415, dated June 15,1897.

Application filed August 1,1895. Serial No. 557,827. (No model.)

.To all whom it may concern: I have shown a form of my invention in theBe it known that I, CHARLES E. SORIBNER, attached drawing. a citizen ofthe United States, residing at Chi- At a substation A are located atransmitcago, in the county of Cook and State of Illiting-telephone b, areceiving-telephone b, a

nois, have invented a certain new and useful signal-bell b and agenerator b of signaling- Improvement in Telephone-Line Circuits,current of the usual type. Line conductors (Case No. 396,) of which thefollowing is a full, 1 and 2 extend from these appliances to a cenclear,concise, and exact description, refertral station C, where they areconnected with ence being had to the accompanying drawing, the usualapparatus in a telephone-switch- 10 forming a part of thisspecification. I board.

My invention concerns the substation ap- At the substation thetransmitting-teleparatus of metallic-circuittelephone-lines, its phoneI) and the receiving-telephone b are purpose being to so arrange thetelephonic included serially in a conductor uniting the and signalingappliances at the substation as two line-wires l and 2. Thereceiving-tele- I 5 to dispense with all switches without impairphonehere represented has usually a resisting the efiiciency of operation ofeither of the ance of about twentyfive ohms and the instruments.transmitting-telephone a normal resistance My invention is particularlyuseful in conof one hundred or two hundred ohms. The nection withtelephone systems in which curbell b is connected in a ground branchfrom 20 rent for exciting the transmitting-telephone conductor 1. Thisbell may havea resistance is supplied over the line-circuit during theof one thousand ohms or more and should be use of the telephone,although it is not limcharacterized by high impedance. The genited tosuch use. erator b is in a similar ground branch from My inventionconsists in including the sigconductor 2 of the line-circuit. It alsoshould 2 5 nal-bell, of high resistance and impedance, in have highresistance and impedance. a ground branch from one of the line conduc-At the central station line conductor 2 is tors and the generator ofsignaling-current, led to ground through an annunciator cl. also of highimpedance, in a similar branch Conductor 1 is here shown groundedthrough from the other line conductor and in placing an impedance-coil6, but so far as my inven- 30 the telephonic appliances in apermanentlytion is concerned it may be left open. Both closed bridge orcross wire of the line-circuit. line-wires are provided with normallyopen At the central station the line-annunciator is terminal contacts ina spring-jack f in the located in that line conductor which includesswitchboard. V the subscribers generator, while the outgoing Theswitchboard is furnished with a pair 3 5 signals from the centralstation are transmitof connecting-plugs g and g, which are united 8 5ted over that line conductor which is more through the helices of aninduction-coil 7L directly connected with the bell at the subthat is,the tips of the connecting-plugs are station. connected together througha conductor 3,

When the substation-generator is operated, which includes the helices hh of the induc- 40 very little of its current finds circuit throughtion-coil, while the sleeves of the plugs form 9:)

the telephone and the call-bell to earth on theterminals of a conductor4, including heliaccount of the high resistance of this path. ces [71721 The point of union of helices h 77. On the other hand, only a smallfraction of and that of helices 7L3 7L4 are connectedtosignaling-current sent from the central stagether through a battery'2', which is designed 45 tion traverses the subscribers generator. tosupply current to-the substation-telephone 5 Then the telephone is inuse, no appreciable during the use of the latter. The strength portionof the telephonic current in the line of this battery may be so adjustedwith relais shunted through the signaling apparatus tion to theannunciator d as not to operate it, on account of the high impedance ofthese inorany well-known device may be employedto 5o struments. preventthe excitement of the annunciator 10o during the connection of thebattery with the circuit-as, for example, the inclusion of a condenserin the ground branch with the annunciator. If desired,- any suitableform of clearing-out annunciator may be employed.

Keys is are included in conductor 4-, the switch-lever of either keybeing adapted, when it is depressed, to open the circuit of thisconductor and to connect the tip of the corresponding plug with one poleof asource Z of signaling-current.

The subscriber at stat-ion A, by turning his generator 19 may transmit asignaling-current to operate the annunciator d. As before stated, only asmall portion of the generated current will traverse the telephone andcallbell. When, replying to the signal thus transmitted, the operatorinserts the plug g into spring-jackf, the circuit of battery 1' isclosed through the transmitting and receiving telephones at thesubstation, thus supplying current for exciting the transmitter.Fluctuations in the current in the line-circuit produced by thetransmitter are reproduced in the circuit with which plug g may beconnected, through the medium of the inductioncoil h, in a well-knownmanner.

The escape of telephonic current through the ground branches at thesubstation is prevented by the impedance of the instruments in thosebranches. At the same time any deleterious influence on the balance ofthe line which their presence might tend to exercise is prevented bytheir symmetrical connection with the circuit. The impedance of the twoinstruments b and 72 being substantially the same, the electrostaticbalance of the line will not be appreciably disturbed by their permanentconnection with it.

If the operator should desire to signal to subscriber at station A, shewould insert the plug g into the spring-jack f and would then depressthe key 70. The current from the signaling-generator Z would then findcircuit over conductor 1 and through the bell b at the substation.

I claim as new The combination with a metallic-circuit telephone-line,of a transmitting-telephone and a receiving-telephone in a bridgethereof at a substation,a signal-bell in a permanentlyclosed branch fromone line conductor, a magneto-generatorin a branch from the other lineconductor, an annunciator at the central station connected with the lineto receive current from the generator, means for applyingsignaling-current to the line also at the central station to operate thesignal-bell, a source of current adapted for exciting thetransmitting-telephone at the central station and means for connectingthe said source of current with the line;.Whereby switches at thesubstation are avoided, as described.

In witness whereof I hereunto subscribe my name this 13th day of June,A. I). 1895.

CHARLES E. SCRIBNER.

